IgG antibody to Mycobacterium tuberculosis antigen-5 in cerebrospinal fluid and its diagnostic application in tuberculous meningitis

IgG antibody to M. tuberculosis antigen-5 was detected by non-competitive ELISA in cerebrospinal fluid specimens (CSF), from 40 patients with clinical diagnosis of tuberculous meningitis and in 42 patients of non-tuberculous neurological diseases. The geometric mean antibody titer in CSF specimen for tuberculous and non-tuberculous groups were 156 and 8 respectively. The antibody titer in CSF specimens showed no correlation to IgG levels, tuberculin reactor status and duration of chemotherapy in patients with tuberculous meningitis. At a dilution end-point 1:40, the assay had a sensitivity of 84% and specificity of 92%. However at dilution end-point 1:80, the specificity of the assay could be increased to 100% but sensitivity of the assay decreased to 75%. IgG antibody detection against M. tuberculosis antigen-5 by non-competitive ELISA, described in this communication has potential application in the laboratory diagnosis of tuberculous meningitis, particularly in developing countries where the incidence and prevalence of tuberculous meningitis is still high. In culture-negative cases of tuberculous meningitis, non-competitive ELISA could be applied as an alternative diagnostic tool.